The present invention relates to an assembly for mounting onto an electronic enclosure comprising a conductive plastic bezel and a shielded window. The plastic bezel is overmolded onto the periphery of the shielded window in an injection molding process, thereby providing an integrated construction with improved electrical contact between the bezel and the shielded window. As a result, the shielding integrity of the integrated assembly is maintained without the need for additional shielding materials which would be required if separate parts were used. The bezel permits an environmental seal and electrical contact to be maintained between the bezel and the shielded window for improved EMI shielding.
As is known in the art, EMI energy is energy that is radiated or conducted from a source, and adversely affects the performance of an electronic circuit impacted by the radiation. EMI and/or RFI may be eliminated or reduced by the use of shielded enclosures and the use of appropriate shielding materials.
The operation of electronic equipment, such as televisions, radios, computers, medical instruments, business machines, communication equipment, and the like, is typically accompanied by the generation of radio frequency and/or electromagnetic radiation within the electronic circuits of the electronic system. The increasing operating frequency in commercial electronic enclosures, such as computers and automotive electronic modules, results in an elevated level of high frequency electromagnetic interference (EMI). The decrease in size of handheld electronic devices, such as cellular phone handsets, has exacerbated the problem. If not properly shielded, such radiation can cause considerable interference with unrelated equipment. Accordingly, it is necessary to effectively shield and ground all sources of radio frequency and electromagnetic radiation within the electronic system.
Typical EMI protective devices include conductive coatings, EMI shielding gaskets, conductive films, and metalized fabrics, screens and meshes. These devices are deployed to block the transmission of unwanted EMI energy into and out of electronic equipment. Windows containing fine wire mesh and conductive transparent films have been typically used to shield display panels, including displays for electronic devices. Such devices are described in U.S. Pat. Nos. 4,910,090 and 5,489,489, as well as EP 810452, the respective disclosures of which are incorporated by reference herein in their entirety.
Transparent EMI shielding films employing polymers, such as PET, and conductive particles, such as ITO (indium tin oxide), silver and conductive oxides, are available commercially from various suppliers. An example of this type of commercial film is the AgF8 film sold by the Parker Hannifin Corporation (Chomerics Division). AgF8 is a multi-layer conductive, silver-oxide based polyester film which has optical transparency and high electrical conductivity. These films, typically on the order of 175 microns in thickness, are used to shield electronic equipment from EMI and RFI radiation. Electronic equipment which can be shielded in this manner includes, by way of example, electronic displays, membrane switch panels, access panels and windows used for the display of electronic data, i.e. shielded windows.
The shielded window as described above is generally affixed to an electronic device using an interface part, typically a bezel. The bezel is similar to a picture frame and is mounted on the outer periphery of the window. Once mounted on the shielded window, the bezel can be used to affix the window to the electronic device. The primary purpose of the bezel is to secure the shielded window to the device using a physical attachment part, such as a screw or bolt. A gasket having EMI shielding properties can be used to provide an environmentally secure seal between the bezel and the shielded window. The gasket thereby serves to prevent radiation leakage at the sealing juncture. Alternatively, a secure seal can be provided through the use of conductive busbars, foil tapes, extended mesh components of the shielded window, and conductive adhesives, all of which serve to provide electrical conductivity and shielding capabilities.
The type of construction necessary to assemble a bezel and window involves the assembly of two or more separate parts, which is costly and labor intensive. This type of assembly is also prone EMI leakage problems, and is costly to repair and replace.
Accordingly, it is an objective of the present invention to provide an improved shielded window assembly that is simple to manufacture, has superior performance characteristics, and is easier to mount to an electronic device as compared to existing assemblies.